Showing papers on "Chemical bath deposition published in 1998"

Developing an understanding of the processes controlling the chemical bath deposition of ZnS and CdS

Abstract: The deposition of cadmium sulfide by chemical bath methods is straightforward and involves an alkaline solution of a cadmium salt, a complexant and a chalcogen source, often thiourea or thioacetamide. Supersaturation of the bath with respect to ‘Cd(OH) 2 ’ is necessary for the deposition of good quality films under a wide range of conditions. In contrast zinc sulfide is more difficult to deposit. In this paper we discuss the literature concerning the deposition of these chalcogenides and use equilibrium models to rationalise many of the observations found in the literature. Strategies for the deposition of high quality films of ZnS by CBD are discussed.

CdS photoluminescence inhibition by a photonic structure

Abstract: Here we present experimental evidence of the strong modification of the CdS photoluminescence when it is embedded in a SiO2 colloidal photonic crystal. When the emitted light matches a forbidden photonic band in the matrix, inhibition of the semiconductor photoluminescence is achieved. In this work we prove the effective control of this effect by means of the photonic lattice parameter of the host. CdS was grown by chemical bath deposition and its quality has been checked employing Raman spectroscopy and x-ray diffraction. Scanning electron microscopy is used to study the morphology of the composite.

Preparation of Indium Hydroxy Sulfide In x ( OH ) y S z Thin Films by Chemical Bath Deposition

Abstract: Indium hydroxy sulfide thin films have been prepared by chemical bath deposition using indium(III) chloride, acetic acid, and thioacetamide. Deposition time, acetic acid, and thioacetamide concentrations have been varied in order to study the influence of these parameters on the chemical deposition process, thin-film composition, and optoelectronic and morphological properties. A decrease in the homogeneous reaction starting time occurs for increasing thioacetamide concentration, but an opposite response is observed as acetic acid concentration is increased. Increasing thioacetamide and acetic acid concentrations results in a decrease in the average optical transmission for both visible and infrared intervals. X-ray photoelectron spectroscopic analysis suggests the film is a nonstoichiometric In x (OH) y S z compound. Bandgap values between 2 and 3.7 eV and resistivity values of 10 7 to 10 8 cm have been obtained. Atomic force microscopy images reveal that lower thioacetamide and higher acetic acid concentrations lead to a larger grain size in the deposits.

Preparation of crystalline cdse particles by chemical bath deposition

Abstract: Crystalline CdSe particles were prepared by keeping the precursor solutions at temperatures above 60 °C. It was essential to use sodium sulfite as a stabilizing agent for selenium ions and sodium dicarboxylate as a complexing agent for cadmium in the precursor solution. The principal crystalline phase of the samples obtained at 60 °C was a cubic zincblende-type phase, but those prepared at 80 °C coexisted with a hexagonal wurtzite-type phase. The ratio of cadmium to selenium in the samples decreased with an increase of the concentration of selenourea in the precursor solutions, irrespective of the kind of complex agents and the keeping time of the precursor solutions. The band-gap energy of CdSe with an atomic ratio (Cd/Se) of 1 showed a value of 1.74 eV, but that with the ratio of 2.3 gave a slightly smaller value of 1.42 eV.

13·7%-Efficient Zn(Se,OH)x/Cu(In,Ga)(SSe)2 thin-film solar cell

Abstract: Cu(In,Ga)Se2 (CIGS) and related semiconducting compounds have demonstrated their high potential for high-efficiency thin-film solar cells. The highest efficiency for CIGS-based thin-film solar cells has been achieved with CdS buffer layers prepared by a solution growth method known as chemical bath deposition (CBD). With the aim of developing Cd-free chalcopyrite-based thin-film solar cells, Zn(Se,OH)x buffer layers were deposited by CBD on polycrystalline Cu(In,Ga)(S,Se)2 (CIGSS). A total-area conversion efficiency of 13·7% was certified by the Frauenhofer Institute for Solar Energy Systems. The CIGSS absorber was fabricated by Siemens Solar Industries (California). For device optimization, the thickness and good surface coverage were controlled by XPS–UPS photoemission spectroscopy. A Zn(Se,OH)x thickness below 7 nm has been found to be optimum for achieving a homogeneous and compact buffer film on CIGSS, with open-circuit photovoltage Voc=535 mV, fill factor FF=70·76% and a high short-circuit photocurrent density Jsc=36·1 mA cm−2. Copyright © 1998 John Wiley & Sons, Ltd.

Method for obtaining a sulfur-passivated semiconductor surface

Abstract: An aqueous thiourea-ammonia treatment is used to form a thin sulfurous film at the indium phosphide surface, having a thickness of less than one nanometer. The thiourea-ammonium hydroxide treatment can be used as is or immediately prior to deposition of cadmium sulfide for enhanced surface passivation. The thiourea-ammonium hydroxide treatment is entirely compatible with chemical bath deposition, molecular beam epitaxy, or metalorganic chemical vapor deposition of the cadmium sulfide.

Incorporation of Cadmium Sulfide into Nanoporous Silicon by Sequential Chemical Deposition from Solution

Abstract: The incorporation of cadmium sulfide into porous silicon is investigated with the aim of realizing electrical contacts with the inner surface of the porous material. This is achieved by using a sequential chemical bath deposition method, consisting of the deposition O a few monolayers of cadmium hydroxide in a first solution, and conversion into cadmium sulfide in a second solution containing thioacetamide. This sequence is repeated five times until the pores are completely full. The chemical deposition process is assessed by a detailed analysis of the solution chemistry. Characterizations of the deposit by scanning electron microscopy, X-ray fluorescence, Auger electron spectroscopy, Rutherford back scattering, and X-ray photoelectron spectroscopy are presented and confirm good pore penetration by CdS, with only a weak concentration gradient from the top to the bottom of the porous layer.

Chemical bath deposition of mercury(II) sulfide thin layers

Abstract: Thin layers of mercury(ii) sulfide have been prepared by a newly developed chemical bath deposition technique. The layers were grown on glass substrates previously coated with a very thin layer of lead sulfide (thickness <10 nm). The deposition was performed in alkaline media at 65 °C from thiosulfate complexes of mercury. X-Ray investigation indicates that the deposited material is a mercury(ii) sulfide mixture of two phases, α-HgS and γ-HgS, with α-HgS dominant. The optical bandgap,Eg, was evaluated from VIS absorption spectra and found to have a value of 3.1 eV.

Comparison of CdS thin films prepared by different techniques for applications in solar cells as window materials

Abstract: CdS thin films as window materials for solar cells have been prepared by three procedures; chemical bath deposition, electrodeposition in an aqueous medium at 80 °C and electrodeposition in a non-aqueous medium at 170 °C. As deposited films along with those obtained after annealing in air at 400 °C for 15 min were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), glow discharge optical emission spectroscopy (GDOES), scanning electron microscopy (SEM), optical absorption spectra and photoelectrochemical spectroscopy (PEC) techniques under identical experimental conditions. X-ray diffraction data indicate the formation of hexagonal CdS as the predominent phase, but the SEM studies show that their textures are widely dependent on the conditions employed. GDOES profiling indicates the incorporation of Na and Si into CdS films prepared by all three techniques. Annealing of chemical bath deposited films causes a red shift of the absorbance edge and also a shift in the maxima of the photocurrent action spectra towards the low energy side. However, this effect was comparatively negligible for the samples prepared by the other two techniques. PEC studies indicate that CdS materials grown by all three techniques are all n-type. All studies indicate that the films grown at 170 °C using non-aqueous solutions are of better crystallinity and of improved electrical properties. © 1998 Kluwer Academic Publishers

Anodic formation of binary and ternary compound semiconductor films for photovoltaic cells

Abstract: By anodic oxidation of copper sheets in sulfide anion-containing electrolytes copper chalcogenide semiconductor films suitable for photovoltaic applications can be attained. Anodically chalcopyrite (Cu2S) has been formed as pure, mechanically stable, homogeneous and adhesive polycrystalline films, consisting of well-developed large crystallites. Cu2S coated copper sheets were produced with an area of 3cm*3cm. P-n-junctions formed by evaporation of CdS onto the anodically formed Cu2S films show an energy efficiency of 3.3. The extension of this process to ternary systems, like copper/indium/sulfur, is likely to be possible. A mixture of Cu2S and CuInS2 could be formed by codepositing In2S3 together with Cu2S. Cu2Se-films with a thickness of up to 1 mum were formed by chemical bath deposition.

Temperature growth and annealing effects on CdS thin films prepared by chemical bath deposition process

Abstract: Homogeneous and strongly adherent CdS very thin films of about 70 nm are elaborated by the chemical bath deposition process. Structural, morphological, optical and electrical properties of the obtained layers are studied for different bath temperatures and after thermal annealing. An important change in the preferred orientation of CdS structure, from (002) to (101), with temperature growth and annealing treatment is reported. The films were resistive and highly transparent with an energy gap value of about 2.37 eV.